1. Field of the Invention
The present invention relates to a brake system, and more particularly, to a hydraulic brake system capable of reducing pressure pulsation that is generated by a piston pump driven by a hydraulic motor upon operation of a brake system.
2. Description of the Related Art
A hydraulic brake system is essentially mounted on a vehicle, and a variety of systems for obtaining a stronger and more stable braking force have recently been proposed.
Examples of a hydraulic brake system include an Anti-lock Brake System (ABS), a Brake Traction Control System (BTCS), and a Vehicle Dynamic Control System (VDC). The ABS prevents wheels from skidding upon braking. The BTCS prevents slip of driving wheels against sudden departure or sudden unintended acceleration of a vehicle. The VDC stably maintains a driving state of a vehicle by controlling a brake oil pressure through a combination of the ABS and the BTCS.
Such a hydraulic brake system includes a master cylinder for generating a pressure necessary for braking, a plurality of solenoid valves for controlling a braking hydraulic pressure transmitted to a wheel brake of a vehicle, a low pressure accumulator for temporarily storing oil, a pump and a motor for forcibly pumping the oil stored in the low pressure accumulator, an orifice for reducing the pressure pulsation of the oil pumped by the pump, and an Electronic Control Unit (ECU) for electrically controlling the operations of the solenoids and the pump.
The valve assembly of the solenoids, the accumulator, the pump, and the motor are compactly installed in a hydraulic block (modulator block) made of aluminum, and the ECU is provided with an ECU housing in which the coil assembly of the solenoid valves and a circuit board are embedded, and is coupled to the hydraulic block.
However, in the conventional hydraulic brake system, as described above, rapid pressure pulsation generated by the driving of the pump in the process of increasing the braking pressure is reduced by the orifice provided in a discharge port side of the pump. Since this is achieved by a configuration that adjusts a cross-sectional area of a passage simply in order to reduce a damping, there is a limitation in completely reducing pressure pulsation.
In addition, another method for reducing pressure pulsation is to increase the number of pistons of a pump. This method increases the overall performance of a motor and the weight and volume of a module, leading to an increase in a manufacturing cost of the pump.
If a peak of pressure pulsation caused by the driving of the pump is successively generated, it may cause the generation of operating noise in a brake system.